Telephone-exchange system



W. H. HARRISON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 9, I918.

Patented Apr. 20, 1920.

UNITED STATES PATENT OFFICE.

WILLIAM H. HARRISON, or BROOKLYN, NEW YORK, ASSIGNOR TO wris'rnnnnnnornrc COMPANY, mconronsrnn, on NEW YORK,- N. Y., A. conronA'rlolv OF NEW YORK.

TE EPHONE-EXCHANGE SYS EM.

Specification of Letters Patent.

Patented Apr. 20, 1920.

Application filed May 9, 1918, Serial No. 233,450.

To all whom it may concern Be it known that I, VILLIAM H. HAR- RISON, a citizen of the United States, residing at Brooklyn, in the county of Kings, State or New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and. exact description.

This invention relates to telephone exchange systems, and more particularly to such systems of the central energy type.

The object of this invention is to provide improved signaling means for such systems.

In accordance with this invention a central office link circuit is provided with a relay which is energized upon each energiz'ation of the link circuit supervisory relay,

and deenergized upon each deenergization thereof, and a third relay which is energized upon the deenergization of the supervisory relay, and with interrupter mechanism which is connected in circuit with a signaling device associated with the link circuit when all three of the relays are energized. For a more complete, understanding of: this invention, reference should be had to the following description considered in connection with the accompanying drawing illustrating one embodiment thereof.

As shown in the drawing two telephone lines A and B terminate at a central oflice at which is located a link circuit C for connecting together lines for conversation. It will be understood, of course. that many lines similar to A and B may terminate at the central oflice, and that number or link circuits similar to C may and usually are provided for interconnecting such lines. However, for the purpose or simplicity, only the two lines and the one link circuit are shown. It is thought that the nature of this invention is such that it will be thoroughly understood from a description of the operation or the system disclosed in the drawing, and it will be so described.

Subscriber A, in initiating a call, removes the receiver the switchhook, thereby causing the lighting of line lamp 5. The operator, observing the lighted. condition of this line lamp 5, inserts answering plug 6 into line jack 7, thereby causing the normally closed contacts or the jack 7 to be opened to remove the ground connection and the line lamp connection from the line,

thereby to efiace the line lamp. Supervisory relay 8 also operates upon the connection of the answering plug with the line jack, and in operating, causes the operation of relay 9 over a circuit from battery through the winding of relay 9', contact 10 thereof, alternate contact of relay 8, sleeve contacts of the plug 6 and the jack 7 and resistance 12 to ground. Relay 9, in operat ing, completes a locking circuit for itself which may be traced from battery through the winding of relay 9, contact 13 thereof. contact 1 4; of relay 15, sleeve contacts of the plug 6 and the jack 7 and resistance 12 to ground. The operator may now actuate listening key 16 to connect the telephone set with the talking strands of the cord circuit C. Upon being advised that connection is desired with the line of subscriber B. the operator restores listening key 16 to normal position and inserts plug 20 into jack 21, whereupon calling supervisory lamp 22 is lighted over a circuit from battery through the lamp 22, contact of calling supervisory relay 23, sleeve contacts of the plug 20 and the jack 21 and resistance 24 to ground. The insertion of the plug into the jack also causes the disconnection of the line lamp from the line. The called-for subscriber may now be signaled by actuating ringing key 25 to connect a source of ringing current 26 with the line for operating the usual call bell at the station, after which the ringing key may be restored to normal position. Subscriber B, in respond,- ing to the operation of the call bell, removes the receiver from the switchhook. thereby causing the operation of the calling supervisory relay 23 which opens the circuit of and extinguishes calling supervisory lamp 22.

At the conclusion of the conversation, the subscribers restore the receivers to the si'v'itchhooks, thereby causing the deenergijzation of the supervisory relays 8 and 23, which in releasing their arm atures, close opcrating circuits for answering supervisory lamp 27 and calling supervisory lamp 22. These lamps are thereupon lighted to furnish disconnect signals. The operator may then withdraw the plugs from the acks'. restoring all apparatus to normal condition.

Assuming, however. that subscriber A, after finishing the conversation with subscriber B and before the operator has with drawn plug 6 from the jack '7, desires to initiate another call, the removal of the receiver from the switchhook after its restoration thereto, causes the intermittent operation of the answering supervisory lamp 27. This intermittent operation of the answering supervisory lamp 27 which serves as a recall signal to the operator, is brought about in the following manner. Upon the restoration of the receiver to the switchhook by subscriber A and the consequent deenergization of the answering supervisory relay 8, relay 15 operates over a circuit from battery through the normal contact of listening key 16, winding of relay 15, contact 30 thereof, contact 31 of relay 9, normal contact of relay 8, sleeve contacts of the plug 6 and the jack 7, and resistance to ground. Relay 15, in operating, establishes a locking circuit for itself which may be traced from battery through the normal contact of the listening key 16, winding of relay 15, contact 32 thereof, sleeve contacts of the plug 6 and the jack 7, and resistance 12 to ground. The establishment of this locking circuit renders relay 15 independent of the condition of either the answering supervisory relay 301- the relay 9. The opening of contact 14 of relay 15 interrupts the locking circuitot relay 9 which now releases its armatures. The closure of contact 33 of relay 15 connects interrupter 35 with the open contact 31' of relay 9. The subsequentenergization of the supervisory relay 8 causes the operation of relay 9over a circuit from battery through the winding and contact 10 of relay 9, alternate contact of relay 8, sleeve contacts of the plug 6 and the jack 7 and resistance 12 to ground. Contact 13 of relay 9 is closed before contact 10 opens, so that a holding circuit for relay 9 is established upon its energization. This holding circuit "may be traced from battery through the Winding and contact 13 ofrelay 9, contact 34 of relay 15, alternate contact of relay 8, sleeve contacts of the plug 6 and the jack 7, and resistance'12 to ground. The closure or" contact 31 of relay 9 connects the interrupter 35 in circuit with'the lamp 2?,

thereby causing the intermittent operation of this lamp.

Theoperator, observing the intermittent lighting of the supervisory lamp 2'? actuates listeningkey 16 to connect the operators telephone set with the talking strands of the "cord circuit. Upon the operationof this listening key 16, the normally closed contact thereof is opened,whereupon relay 15 is deenergized. Relay 15, in releasing its armatures, disconnects the interrupter 35 from circuit relation with the lamp 27, thereby stopping the intermittent lighting of this lamp. Relay 15, in releasing, also causes the deenergization of relay 9,'but this relay, 1mmediately upon releasing its armatures, establishes its original energizing cir cuit. Upon this re'e'nergization of relay 9, its locking circuit is established in the manner before described,

What is claimed is: V

1. A telephone exchange system comprising a telephone line, a link circuit connected therewith, a supervisory relay for the link circuit, 'a second relay operating upon the energization of the supervisory relay, a third relay energized upon the denergiza tion of the supervisory relay to release the second relay, a signaling device, and interrupter mechanism connected in circuit with the signaling device by the subsequent operation of the second relay when the super visory relay is energized.

2. A telephone exchange system comprising a telephone line, a link circuit connected therewith, a supervisory relay for-the link circuit, a second relay operating upon the energization of the supervisory relay, third relay energized upon the deenergization of the supervisory relay to release the second relay, a signaling device, interrupter mechanism, and an operating circuit for the signaling device and interrupter mechanism established upon the subsequent operation of the second relay and including engaged con tacts of the energized second and third relays.

3. A telephone exchange system comprising a telephone line, a link circuit connected therewith, a supervisory relay for the link circuit, a second relay operating upon the energization of the supervisory relay, a third relay, a locking circuit for the second relay established upon theoperation thereof and including a contact of thevdeenergized third relay, an energizing circuit for the third relay established upon the de'e'nergization of the supervisory relay and including a contact of the operated second relay thereby to release the second relay, a signaling device, and interrupter mechanism included in circuit with the signaling device-by the subsequent operation of the second relay when the supervisory relay is energized. Y

1. A telephone exchange system comprising a telephone line, a link circuit connected therewith, a supervisory relay for the link circuit, a second relay operating upon the energization of the supervisory relay, a third relay, a locking circuit for the second relay established upon the operation thereof and including a contact of the deenergized third relay, an energizing circuit for the third relay established upon the deenergization of the supervisory relay and including a contact of the operated second relay thereby to release the second relay, a signaling device, interrupter mechanism, and an operating circuit for the signaling device and interrupter mechanism established upon the subsequent operation of the second relay and including engaged contacts of the energized second and third relays.

5. A telephone exchange system COI11PllS ing a calling telephone line, a link circuit connected therewith a supervisory relay for the link circuit energized upon the closure and deencrgized upon the opening of the telephone line, a second and a third relay for the link circuit, an energizing circuit for the second relay closed upon the first energization of the supervisory relay, a locking circuit for the second relay completed upon the energization thereof and including con tact of the deenergized third relay, an energizing circuit for the third relay established upon the de inergization of the supervisory relay and including a contact of the ener gized second relay, the energization of the third relay opening the locking circuit of the second relay, a locking circuit for the third relay completed upon the energization thereof, signaling device, interrupter mechanism, and an operating circuit for the signaling device and interrupter mechanism completed upon the second energization of the supervisory relay and including con tacts ot the energized second and third rclays.

6. A. telephone exchange system comprising a telephone line, a link circuit connected therewith, a supervisory relay for the link circuit energized upon the closure and decnergized upon the opening of the telephone line, a second relay energized upon the energization and de'e'nergized upon the de'energization of the supervisory relay, a third relay energized upon the energization of the second relay when followed by the cleanergization of the supervisory relay, a'signaling device and interrupter mechanism, and an operating circuit therefor established when all three relays are energized and including contacts of the second and third relays.

In Witness whereof I hereunto subscribe my name this 3rd day of May, A. D. 1918.

WILLIAM H. HARRISON. 

